Casting result of Dictionary of objects after Skip and Take

Question

I have a Dictionary of objects defined like this -

Dictionary<string, MyObject> myObjectDictionary 

I would like to grab items in the Dictionary based of an index and count of items. I am trying to use Skip and Take. But this requires recasting it back to Dictionary<string, MyObject>. How can this be done? Is there a different way I should be doing this?

Here is my code and failed attempt to recast -

Dictionary<string, MyObject> myObjectDictionary = FillMyObjectDictionary();

var mySmallerObjectDictionary = myObjectDictionary.Skip(startNumber).Take(count);

//THE FOLLOWING DOES NOT WORK
Dictionary<string, MyObject> myNewObjectDictionary = (Dictionary<string, MyObject>)mySmallerObjectDictionary  

Answer 1

Well, you can create a new dictionary:

Dictionary<string, MyObject> myNewObjectDictionary =
    myObjectDictionary.Skip(startNumber)
                      .Take(count)
                      .ToDictionary(pair => pair.Key, pair => pair.Value);

However:

• You shouldn't rely on the ordering of a dictionary. It's not clear which items you wish to skip. Consider using OrderBy before Skip. For example:

  Dictionary<string, MyObject> myNewObjectDictionary =
      myObjectDictionary.OrderBy(pair => pair.Key)
                        .Skip(startNumber)
                        .Take(count)
                        .ToDictionary(pair => pair.Key, pair => pair.Value);
  

• This does not preserve any custom equality comparer that was in the original dictionary. Unfortunately that's not exposed anywhere, so you'll just have to know whether or not FillMyObjectDictionary uses a custom comparer.

Answer 2

The result of the Skip / Take operation will not be an IDictionary<string, MyObject>, it will be an IEnumerable<KeyValuePair<string, MyObject>>.

If you want to convert this back to a dictionary, try calling ToDictionary:

var myNewObjectDictionary = mySmallerObjectDictionary.ToDictionary(p => p.Key, p => p.Value);